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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

VARIEGATED, ORANGE AND BUTLER GLACIERS
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hornblende gneiss near the valley mouth on both sides, and above this, green argillite schist, white granite, and red, orange,and banded-gray gneiss that on exposure to weather rusts to different colors. All these rock types were present in the angular moraine that was strewn in bands and patches over the lower portion of the valley glacier.
The Expanded Bulb in 1906. On emerging from its valley (Map 8, in pocket), Variegated Glacier expanded in a broad, bulb-shaped piedmont area, which was evidently completely stagnant. This bulb spread westward until it coalesced with Hubbard Glacier, and southward almost to the fiord. Throughout the piedmont bulb the surface was almost completely covered with ablation moraine, increasing in thickness toward the periphery.1 The piedmont area consisted of three quite different parts: (1) just beyond the valley portion of the glacier an expanded bulb mostly covered by a series of crescentic moraine ridges of different colors,8 though with ice appearing here and there in small areas; (2) a crescentic interior flat mainly of gravel, but with ice beneath; and (3) an outer, much larger area so deeply covered with moraine that ice showed in only a few places.
The Inner Bulb. Between the interior flat and the valley glacier the inner bulb began abruptly in a steep ice wall rising fully 100 feet above the partially debris-veneered portion of the valley glacier. This slope
rose up to a ridge whose crest                      ,   \   \ \ I
was covered with blocks of a gray quartz gneiss which on exposure to the weather rusted to an orange yellow, giving to the moraine ridge a distinct orange tinge noticeable at a distance of 7 or 8 miles. This orange moraine ridge was crescentic in form with the concave side upstream, and on its eastern end it merged into the eastern lateral moraine of the valley part of the glacier.
Outside the orange moraine, down as far as the interior flat, were a succession of valleys and ridges, all crescentic in form (Fig. 7). The valleys were located in areas of thin moraine, while the ridges marked the sites of thicker morainic accumulation; but nowhere was the moraine thick. The crescentic ridges, whose radius increased toward the interior flat, were notably different in color. That next the orange moraine was greenish in color,
»For a more detailed description of this piedmont area, see Tarr, R. S., The Yakutat Bay Region, Alaska, Professional Paper 64, TJ. S. Geol. Survey, 1909, pp. 47-49. • First observed and described by Gilbert in 1899.
FIG. 7. Sketch map of banded moraines of Variegated Glacier in 1905. A, White granite moraine; B, red rusted moraine; 0, hornblende gneiss moraine; D, interior fiat; E, red moraine; F, purple moraine; 5, green moraine; H, orange moraine; I, ice surface; J, beach; K, glacial stream, 1905; L, glacial stream, 1906; Mt highest^point reached in 1905.